Engine misfire

CHRISTINAGALE2

MEMBER
1999 KIA SEPHIA
4 CYL
2WD
AUTOMATIC
150,000 MILES

About six months ago it had a misfire in cylinder three. When scanned it also showed a bad speed sensor code and bad catalytic converter code. I replaced all four spark plugs, wires and coils and put in a new speed sensor. I did not, however replace the catalytic converter. Now, my car has a rough idle and tends to run rough until it goes into third gear. It also is having trouble with hills. I had it scanned again and there is now a misfire on cylinder two and the speed sensor code (P0501) is coming up again (the speed sensor code was cleared after it was repaired.) Along with the catalytic converter code. I was wonder if the faulty catalytic converter is causing the misfires to happen and taking out the speed sensor? I also now have the P1624 code, but I have not had transmission codes checked, not sure if it could also be related to the catalytic converter?

1 Reply

STEVE W.

MECHANIC
13,452 POSTS

A bad catalytic converter will not set a speed sensor code. But depending on how it has failed it can cause the misfire codes. If it is due to it starting to plug up it will not let the exhaust exit properly and the exhaust will back up into the cylinders and cause a misfire. It is also possible that the cylinder two miss is due to a bad plug or wire. If you have the old parts you could try replacing one at a time and see if the miss goes away.

P1624 is a code to tell you that you have fault codes stored in the transmission.
The VSS code could be the reason for that code or there may be others as well.
P0501 is for an intermittent or "jumpy" signal, like it shorts out and then reads proper. Many times it is not due to a bad sensor but due to bad wiring from the sensor.